Exactly. We get our English word "planet" from that word, but in Greek "planetes" means "wandering star." It only appears once in the Bible, in Jude 1.13 (as per the OP's question), combined with ἀστέρες πλανῆται, meaning "wandering stars." They didn't know what the planets were, that they weren't stars, and exactly why they behaved as they do. "Planetes" means "wanderer."

> The Greeks and Romans had no word for planet.

That doesn't look right. There was the Greek word 'planetes'

The Greeks and Romans had no word for planet. They had no understanding of planets. How do you expect an author from that culture and time to use a word that didn't exist to describe a concept that didn't exist?

There is no new scientific revelation in the Bible. Not a single statement in the Bible offered to its original audience any new insight into how the material world regularly works or how the naturalistic cause-and-effect system works. Instead, the perspectives on the material (natural) world we find in the text accommodate the Old World science of the time and are part of the words, phrases, and genres adopted in order to communicate clearly to the target audience. After all, some understanding of the world and its operations had to be used in some discussions in the text. Why would we think that the human communicator would use the science of our day? In fact, that would be foolishness because a century from now we will undoubtedly have adopted some new scientific conclusions that differ from what we believe today. Science is always changing, and is expected to continue changing. God chose human communicators associated with a particular time, language, and culture and communicated through them into that world, and indirectly to us. It has information for us as we are able to penetrate the message being conveyed by the human communicators to their audience.

If God had communicated modern scientific information to the ancient audience, it would have communicated NOTHING. God accommodated their scientific beliefs in order to communicate. Those concepts are not vested with authority. The authority is in the message, not in the terminology or the scientific understanding of the day.

So, it's as scientifically inaccurate as confusing a whale with a fish and simultaneously defending the Bible as the infallible word of God. I know the Bible isn't a science text book, but come on.

Back in the days of the Bible, the ancients didn't know what the planets were. They called them "wandering stars," noticing the pattern of their movement different from other stars, but thinking they were a form of star. They didn't know anything about our solar system. Venus was called the morning star. They detected a prescribed path in the planets, but didn't understand what kind of "star" it was, since these few items were different from all the others.

The fallen-away former Christians were perceived to be like that. They didn't belong to the regular system. They strayed from the usual pattern.

"Wandering stars" are an anology for fallen away former Christians. But stars and planets, the ones we can measure anyway, follow a prescribed path. How is this a useful analogy when planets don't wander about but rather orbit in a fixed manner?